1. Field of the Invention
The present invention relates to a magnetic field modulation use magnetic head, a magneto-optical element, and an optical pickup devices used for an optical disk drives for recording or playing back a magneto-optic signal to or from a magneto-optic recording medium and to such an optical disk drive.
2. Description of the Related Art
In recent years, the advances made in the technology for digitally recording moving pictures, static images, or other video data have led to large volumes of data being handled, so magneto-optic disk drives and other optical disk drives utilizing magneto-optic recording capable of further raising the recording density have spread in use in place of floppy disk drives and other magnetic disk drives which have been conventionally generally been widely utilized.
For example, when a magneto-optic disk drive, one type of optical disk drive, records data, it focuses a laser beam on a position on the magneto-optic disk for recording the data to make the temperature of the magnetic material (magneto-optic recording layer) at that position rise up to the Curie temperature and cancel out the coercive force corresponding to data already recorded at that position and further applies a magnetic field corresponding to the data to be newly recorded to that position (position at which the temperature has become the Curie temperature) to thereby record the data.
For example, in the Mint Disc (MD) system or the like which have been already put into practical use as optical disk drives for recording and playing back of information data with respect to a recording medium, here a magneto-optic disk, by a magnetic field modulation system, a magnetic field generation coil (magnetic head) for applying a magnetic field at the time of recording data is arranged at a position facing the optical pickup device emitting the laser beam across the disk.
The magnetic field generation coil and the optical pickup device move to positions for recording the data on the optical disk, then the magnetic field generation coil applies the magnetic field to the predetermined position and the optical pickup device emits the laser beam.
Further, in recent years, as an optical disk drive for recording and playing back of information data with respect to a recording medium, that is, magneto-optic disk, by the magnetic field modulation system, there have been proposed for example a near field optical disk drive made by Tera Stor Co. for recording and playback while arranging the optical disk and the optical lens at a distance between them becomes 200 nm or less, an optical hard disk drive made by Quinta Co. in which the optical lens is mounted on a floating type slider, and other optical disk drives arranging the optical disk and the optical lens or a slider mounting the optical lens or the like at a distance of 200 nm or less to make it possible to raise the numerical aperture NA and further raise the recording density.
In the above near field optical disk drive or other optical disk drive raising the numerical aperture NA, in order to secure an optical skew margin when the numerical aperture NA is raised and a margin of the thickness of the optical disk substrate, the recording layer is arranged on the optical lens side of the optical disk substrate.
In the above optical disk drive, when arranging the magnetic field generation coil at the side of the optical disk opposite to the optical lens, if the inductance of the magnetic field generation coil is made small, that is, the diameter of the magnetic field generation coil is made small, in order to enable a high speed transfer of a large volume of data such as a video signal, it becomes difficult to apply an effective magnetic field of for example about 200 Oe to the recording layer of the optical disk since the spread of the magnetic field is large. Accordingly, in order to make it possible to transfer a large volume of data at a high speed, it becomes necessary to arrange the magnetic field generation coil for applying the magnetic field to the recording layer of the optical disk on the same side of the optical disk as the optical lens.
Further, by integrally constituting the magnetic field generation coil and the optical lens, a reduction of the thickness of the optical disk drive has become possible.
An explanation will be made next of a magneto-optical element integrally constituting the magnetic field generation coil and the optical lens.
FIG. 9 is a plan view of the configuration of a magnetic coil 46 part of a magneto-optic head portion according to the related art, which can be applied as a magneto-optic head of a magneto-optic disk system.
A spiral-shaped thin film coil 48 having a size of for example an inner diameter of 50 to 200 xcexcm and an outer diameter of about 350 to 400 xcexcm is formed on the periphery of an emitting portion 44d of a coil supporting substrate 44 on a main surface of the coil supporting substrate 44 facing the magneto-optic disk. The thin film coil 48 is covered by an insulation layer 49.
Further, a magnetic core 47a is formed on the coil supporting substrate 44 beneath of the thin film coil 48. The magnetic core 47a acts also as an electrode takeout portion inside the spiral shaped thin film coil 48.
The emitting portion 44d region is the region from which the laser beam L emitted from a not illustrated semiconductor laser is emitted. In this region, an aperture portion Ha is formed in the magnetic core 47a and becomes the optical axis of the laser beam L.
The magneto-optical element integrally constituting the magnetic field generation coil and the optical lens emits the laser beam L from the emitting portion 44d to the magneto-optic recording layer of the magneto-optic disk and, at the same time, can apply a magnetic field generated by the thin film coil 48 and therefore can record and play back information with respect to the magneto-optic recording layer of the magneto-optic disk.
Summarizing the problems to be solved by the invention, in the optical disk drives of the MD and other magnetic field modulation systems which have already been put into a practical use, however, a bulk head is used for the magnetic head for generating the modulation magnetic field, so it has been difficult to raise the modulation frequency.
Further, in a magneto-optical element raising the numerical aperture by integrally constituting the magnetic field generation coil and the optical lens shown FIG. 9, It is necessary to provide the magnetic field generation coil at an outer circumferential portion of the emitting portion region serving as the optical axis of the laser beam and it is necessary to set the diameter of the magnetic field generation coil to a predetermined value or more, therefore it was not possible to configure the magnetic head to improve the efficiency of the magnetic circuit as was used in for example magnetic recording and it was difficult to apply the magnetic field to the recording layer of the optical disk with a low power consumption and a high efficiency.
Further, in order to generate the required magnetic field at the time of recording, a very large current must be passed through the magnetic field generation coil, therefore the amount of heat generated in the magnetic field generation coil becomes large, and, in the worst case, disconnection of the magnetic field generation coil has been sometimes induced.
An object of the present invention is to provide a magnetic field modulation use magnetic head, a magneto-optical element, an optical pickup device, and an optical disk drive capable of applying a magnetic field to the recording layer of an optical disk with a low power consumption and a high efficiency and capable of preventing the disconnection of the magnetic field generation coil due to heat generation.
To attain the above object, according to a first aspect of the present invention, there is provided a magnetic field modulation use magnetic head for applying a magnetic field to a magneto-optic recording layer of a magneto-optic recording medium, comprising a magnetic field generation coil arranged so that a direction of a recording current is substantially parallel to a plane of said magneto-optic recording layer, a first magnetic core formed at a side of said magnetic field generation coil opposite to said magneto-optic recording medium, and a second magnetic core formed at a side of said magnetic field generation coil the same as said magneto-optic recording medium.
In the magnetic field modulation use magnetic head of the present invention, preferably an aperture portion is formed in said first magnetic core at a center region of said magnetic field generation coil, more preferably, aperture portions are formed in said first magnetic core and said second magnetic core at the center region of said magnetic field generation coil, still more preferably, a diameter of the aperture portion of said second magnetic core is made larger than a diameter of the aperture portion of said first magnetic core.
Further, preferably part of said first magnetic core and part of said second magnetic core are magnetically connected at an outer circumferential portion of the coil or the like.
The magnetic field modulation use magnetic head of the present invention has magnetic cores above and below the magnetic field generation coil, so the efficiency of the magnetic circuit rises, it is possible to apply the magnetic field to the recording layer of the optical disk with a low power consumption and a high efficiency, and the disconnection of the magnetic field generation coil due to heat generation can be prevented.
According to a second aspect of the present invention, there is provided a magneto-optical element used in at least recording or playback of information with respect to a magneto-optic recording layer of a magneto-optic recording medium, comprising a lens for focusing light emitted to the magneto-optic recording layer of the magneto-optic recording medium and a magnetic field generating means formed at a surface of said lens facing said magneto-optic recording medium, said magnetic field generating means having a magnetic field generation coil arranged substantially parallel to the magneto-optic recording medium, a first magnetic core formed at a side of said magnetic field generation coil opposite to said magneto-optic recording medium, and a second magnetic core formed at a side of said magnetic field generation coil the same as said magneto-optic recording medium.
In said magneto-optical element of the present invention, preferably said magnetic field generating means is formed on a supporting substrate made of an optical member constituting said lens, and said supporting substrate is fixed to an optical member having a spherical shape constituting said lens.
Further, preferably, said lens Is constituted by a group of a plurality of lenses arranged on an optical axis of the light emitted to said magneto-optic recording medium, more preferably, said lens is constituted by a group of two lenses arranged on the optical axis of the light emitted to said magneto-optic recording medium.
In said magneto-optical element of the present invention, preferably aperture portions are formed in said first magnetic core and said second magnetic core at the center region of said magnetic field generation coil serving as a optical axis of the light emitted to said magneto-optic recording medium, more preferably a diameter of the aperture portion of said second magnetic core is made larger than a diameter of the aperture portion of said first magnetic core.
Further, preferably part of said first magnetic core and part of said second magnetic core are magnetically connected at the outer circumferential portion of the coil or the like.
Since the magneto-optical element of the present invention has the magnetic field generation coil and the magnetic cores above and below it as the magnetic field generating means on the surface of the lens facing the magneto-optical recording medium, the efficiency of the magnetic circuit rises, it is possible to apply the magnetic field to the recording layer of the optical disk with a low power consumption and a high efficiency, and the disconnection of the magnetic field generation coil due to heat generation can be prevented.
According to a third aspect of the present invention, there is provided an optical pickup device used at least in recording or playback of information with respect to a magneto-optic recording layer of a magneto-optic recording medium, comprising a light source for emitting light toward the magneto-optic recording medium; a magneto-optical element having a lens which Is arranged on an optical axis of the light emitted from said light source and focusing said light to the magneto-optic recording layer of said magneto-optic recording medium and a magnetic field generating means which has a magnetic field generation coil arranged substantially parallel to said magneto-optic recording medium, a first magnetic core formed at a side of said magnetic field generation coil opposite to said magneto-optic recording medium, and a second magnetic core formed at a side of said magneto-optic generation coil the same as said magneto-optic recording medium and which is formed at a surface of said lens facing said magneto-optic recording medium; and a light receiving means for receiving a returning light reflected at said magneto-optic recording layer.
In said optical pickup device of the present invention, preferably said magnetic field generating means Is formed on a supporting substrate made of the optical member constituting said lens, and said supporting substrate is fixed to an optical member having a spherical shape constituting said lens.
Further, preferably, said lens is constituted by a group of a plurality of lenses arranged on the optical axis of the light emitted to said magneto-optic recording medium, more preferably, said lens is constituted by a a group of two lenses arranged on the optical axis of the light emitted to said magneto-optic recording medium.
In said optical pickup device of the present invention, preferably aperture portions are formed in said first magnetic core and said second magnetic core at the center region of said magnetic field generation coil serving as the optical axis of the light emitted to said magneto-optic recording medium, more preferably a diameter of the aperture portion of said second magnetic core is made larger than a diameter of the aperture portion of said first magnetic core.
Further, preferably part of said first magnetic core and part of said second magnetic core are magnetically connected at an outer circumferential portion of the coil or the like.
Since the optical pickup device of the present invention has the magnetic field generation coil and the magnetic cores above and below it as the magnetic field generating means on the surface, facing the magneto-optical recording medium, of the lens for focusing the light to the magneto-optic recording layer of the magneto-optic recording medium, the efficiency of the magnetic circuit rises, it is possible to apply the magnetic field to the recording layer of the optical disk with a low power consumption and a high efficiency, and the disconnection of the magnetic field generation coil due to heat generation can be prevented.
According to a fourth aspect of the present invention, there is provided an optical disk drive for at least recording or playing back information with respect to a magneto-optic recording layer of a magneto-optic recording medium, comprising a rotation driving means for driving the magneto-optic recording medium to rotate, a light source for emitting light toward said magneto-optic recording medium, a magneto-optical element having a lens which is arranged on an optical axis of the light emitted from said light source and focuses said light to the magneto-optic recording layer of said magneto-optic recording medium, and a magnetic field generating means which has a magnetic field generation coil arranged substantially parallel to said magneto-optic recording medium, a first magnetic core formed at a side of said magnetic field generation coil opposite to said magneto-optic recording medium, and a second magnetic core formed at a side of said magneto-optic generation coil the same as said magneto-optic recording medium and which is formed at a surface of said lens facing said magneto-optic recording medium, a light receiving element for receiving a returning light reflected at said magneto-optic recording layer, and a signal processing circuit for generating a predetermined signal on the basis of the returning light received by said light receiving element.
Said optical disk drive of the present invention preferably further has an adjustment mechanism for adjusting a relative position of said magneto-optical element with respect to said magneto-optic recording medium and a control unit for controlling said adjustment mechanism according to the signal created in said signal processing circuit.
In said optical disk drive of the present invention, preferably said magnetic field generating means is formed on a supporting substrate made of an optical member constituting said lens and said supporting substrate to fixed to an optical member having a spherical shape constituting said lens, and more preferably, said lens is constituted by a group of a plurality of lenses arranged on the optical axis of the light emitted to said magneto-optic recording medium.
Further, preferably said lens is constituted by a group of two lenses arranged on the optical axis of the light emitted to said magneto-optic recording medium.
In said optical disk drive of the present invention, preferably aperture portions are formed in said first magnetic core and said second magnetic core at the center region of said magnetic field generation coil serving as the optical axis of the light emitted to said magneto-optic recording medium, more preferably a diameter of the aperture portion of said second magnetic core is made larger than a diameter of the aperture portion of said first magnetic core.
Further, preferably part of said first magnetic core and part of said second magnetic core are magnetically connected at the outer circumferential portion of the coil or the like.
Since the optical disk drive of the present invention has the magnetic field generation coil and the magnetic cores above and below it as the magnetic field generating means on the surface, facing the magneto-optical recording medium, of the lens for focusing the light to the magneto-optic recording layer of the magneto-optic recording medium, the efficiency of the magnetic circuit rises, it is possible to apply the magnetic field to the recording layer of the optical disk with a low power consumption and a high efficiency, and the disconnection of the magnetic field generation coil due to heat generation can be prevented.